جستجوی مقالات مرتبط با کلیدواژه « Rhizoctonia solani » در نشریات گروه « گیاهپزشکی »

The seeds of common bean plants (Phaseolus vulgaris) are among the most important food sources worldwide. The plant pathogenic fungus Rhizoctonia solani causes seed rot and seedling damping-off of bean plants and is one of the most important soil-borne pathogens in most cultivation areas of this plant. R. solani plays an important role in reducing the yield and quality of this crop. Biological control is a promising, effective, and sustainable solution for managing soil-borne fungal diseases. The simultaneous use of biological control agents, especially agents with different mechanisms of action, might increases the chance of success in disease management. Indeed, two living agents can show different types of interactions based on their inherent characteristics and ecological conditions. In the current research, the potential of co-application of mycorrhizal fungi and bacterial strains from different taxonomic groups was evaluated on increasing the growth of beans and suppression of bean damping-off.

In this research, the effect of 14 different bacterial strains on the mycelial growth of R. solani was investigated by dual culture and by the volatile compound production tests in the laboratory. The list of bacterial strains included: Bacillus megaterium B15, Bacillus thuringiensis B48Pet, Bacillus subtilis BS (B.s), B. subtilis AS, Lysinibacillus boronitolerans RUPB71 (Lysin), Pseudomonas putida RUP1, Arthrobacter citreus B27Pet, Alcaligenes faecalis 1624, Bacillus pumilus INR7, Bacillus thuringiensis 32B (B.thur), Azotobacter vinelandii RUA1 (Azoto), Delftia tsuruhatensis PIIR (Delft), Stenotrophomonas maltophilia S37 and Bacillus velezensis JPS19 (B.vel). In the dual culture test, B.s, B.vel, Alca, Azoto, Lysin, and Delft strains significantly reduced the mycelial growth of the pathogen. In volatile compounds production test, three strains, Alca, Azoto, and B.thur, significantly reduced the mycelial growth of the pathogen. Four bacterial strains, including B.s, B.vel, Alca, and Azoto, were selected for greenhouse experiment. The selected bacterial strains as separate and combined application with two species of arbuscular mycorrhizal fungi (AMF), including Funneliformis mosseae (F.moss) and Glomus claroideum (G.cla) were investigated for inhibiting the disease caused by R. solani, and for their effect on the growth parameters of bean plants in the presence of the pathogen. The greenhouse experiment was conducted as a completely randomized design with 16 treatments and five replications.

Many of the greenhouse treatments that were applied in this study, significantly reduced the severity of the disease compared to the diseased control. They significantly increased the fresh and the dry weight of the shoots, root fresh weight and root dry weight. Four treatments (F.moss, B.s, Alca and Azoto) significantly enhanced the root length and four treatments (Alca, B.s, B.vel+G.cla and Alca+G.cla) increased the shoot length. In terms of the effect on the disease, the B.s strain was the best treatment, which reduced the disease severity by 36.5% and showed the greatest effect in promoting the vegetative characteristics of the plant. Although the bacterial and mycorrhizal strains showed compatibility in many combined treatments, G.cla+B.vel was the only double treatment that showed an increasing effect on the fresh weight and shoot length compared to the separate applications. The other double treatments did not have an additive or synergistic effect in reducing the disease and improving plant growth. Even in some double treatments, in terms of reducing disease and improving plant growth, a weaker effect was seen than their single treatments. Among different treatments, Alca+G.cla and Alca+F.moss showed the highest and B.s+G.cla showed the lowest mycorrhizal colonization.

The effect of bacteria on mycorrhizal colonization was increasing, decreasing, or null depending on the combination of bacterial and mycorrhizal strains used. In many cases, there was no direct relationship between the amount of mycorrhizal colonization and disease control. Overall, before the commercial use of the combination of biological agents, it is necessary to check their interactions in greenhouse and field experiments and ensure their compatibility and lack of antagonistic effect on each other. If the biological agents present in a consortium are compatible, its biocontrol effect will be more stable, efficient and reliable, and it will be possible to use it in a wider range of variable soil ecological conditions. Moreover, the interaction of individuals within a given consortium is strain-specific, and the results of an experiment on specific strains cannot be generalized to other strains of the same species.

Bell pepper with the scientific name Capsicum annuum L. belongs to the Solanaceae family. Among the major pepper diseases, root rot caused by the fungus Rhizoctonia solani has the economic importance. The common method to control this disease is to use the chemical fungicides. In order to control Rhizoctonia root rot disease of bell pepper, a number of commercial biological agents based on Trichoderma harzianum, Glomus sp. mycorrhizal fungus, Bacillus sp. and Pseudomonas sp. bacteria and three chemical fungicides Tebuconazole, Copper oxychloride and Mancozeb were investigated in greenhouse conditions. The analysis of variance showed that the treatments had significant difference (P≤ 0.01) in all the examined traits. The mean comparisons of the treatments were evaluated based on disease inhibition traits including the length of the necrotic tissue with the largest wound and the disease index and plant growth promotion traits, including plant fresh weight, plant height, root dry weight and shoot dry weight. The treatments of negative control (no pathogen) and fungicide tebuconazole had the greatest effect on most of the traits, and the treatments of Potabarvar and Mycoroot and positive control (with pathogen) had the least effect. Among the biological control treatments, based on the lowest disease index and the lowest wound length, the combination of biological agents, Parsbacil, Probio96, Alkagreen, Trichoran-P and Tricho were ranked respectively. In the study of agricultural traits, biological treatments, combination of biological agents, Parsbacil and Probio-96 showed the highest values. In the management of this disease, apart from the chemical control method (Tebuconazole), the best option with a relatively similar statistical level was Parsbacill combination (SC) containing Bacillus velezensis strain M11-RTS, and Probio-96 containing Bacillus subtilis bacteria (P≤ 0.01).

The use of biocontrol agents is a promising and safe method towards achieving environmental goals for controlling plant diseases. However, due to the lack of stability and appropriate and applicable formulations, the results obtained from the application of these agents, especially in agricultural fields, have not been sufficiently efficient. This study was conducted with the aim of developing a capsule formulation using sodium alginate to increase the viability and improve the performance of Bacillus subtilis. Capsules were prepared using the ionic gelation method. The encapsulation efficiency was estimated to be 99%. The mean size of the wet and dry capsules produced was 2600 and 1000 micrometers, respectively. The effects of ultraviolet radiation on the survival of B. subtilis showed that the bacterium in the capsule state (wet and dry) was more resistant to ultraviolet radiation compared to the non–encapsulated state. With increasing exposure time to ultraviolet light, bacterial cells resistance in the capsule state were greater than in the non–encapsulated state. The results of the thermal resistance examination at different temperatures emphasized the positive role of the capsules in increasing the survival and resistance of B. subtilis compared to the non–encapsulated state. The survival percentage of non–encapsulated B. subtilis after 60 days at 25 and 35 degrees Celsius decreased by 42% and 47%, respectively. However, for the encapsulated B. subtilis, the survival percentage decrease after the same period and temperature was estimated to be 16.5% and 26%, respectively. Greenhouse results showed that the use of B. subtilis capsule formulation reduced disease percentage compared to non–encapsulated B. subtilis and sodium alginate capsules alone. The disease percentage in plants treated with encapsulated B. subtilis was estimated to be 4.44%, while this rate was 73.33% in the control. Plants treated with encapsulated B. subtilis had significant differences in growth indices compared to the control. Growth index changes in relation to different formulations of B. subtilis (encapsulated, non–encapsulated) and sodium alginate capsules alone were significant only for root height. These results emphasize the positive role of using B. subtilis and capsule formulation in controlling damping–off caused by Rhizoctonia solani in tomato plants.

In current research Paenibacillus polymyxa strain N179 was selected based on its previous performance in greenhouse and field condition, and cheap by-products of food industry was used to introduce a best medium for its high quality and low cost cultivation. The growth rate of this bacterium in various media was significantly different. In addition, antagonistic activity of cells from various media either in-vitro or in greenhouse condition was significantly different. The cells from M4 (10 g date pomace, 4 g sesame press cake) and M10 (4 g sesame press cake, 5 g starch) have shown highest inhibition against Rhizoctonia solani fungus. The resistance of cells from media against formulation process and viability during preservation period was assessed and it was found that cells from LB, M9, M7, and M2 media were the most resistant ones during preservation period. Moreover, efficacy of prepared formulations was assessed after three months in greenhouse condition and it was found that formulations made from M5 and LB were the most effective ones in controlling the disease. However, considering all of the results, M9 was shown the best performance.

Rhizoctonia solani Kühn is a soil borne fungus that causes stem canker and black scurf and severely damages crop in various potato growing areas in Iran. The aim of this study was to investigate the pathogenicity of various fungal isolates from different potato growing areas in Iran on the Burren cultivar.

In this study, The pathogenicity of 70 isolates of Rhizoctonia solani from major potato growing areas in Iran including the provinces of Ardabil, Isfahan, Fars, Kurdistan, Kerman, Lorestan and Hamedan was investigated on the potato cultivar ‘Burren’ in completely randomized design experiment under greenhouse conditions.

The analysis of variance showed that the pathogenicity of the isolates was very different at probability level of 1% is significant, and therefore they were divided into different groups.

The isolates of Ardabil-1, Ardabil-5, Isfahan-14, Fars-26, Fars-29, Kurdistan-34, Kurdistan-39, Kurdistan-40, Kerman-47 and Hamedan-66 had the highest pathogenicity, while the  isolates Fars-21, Isfahan-20, Hamedan-65 and Isfahan-18 showed the lowest pathogenicity, respectively.

This experiment was designed to investigate the antagonistic effect of six isolates of two Trichoderma species, i.e. Trichoderma harzianum and Trichoderma viride on growth and eliciting plant defense responses against Rhizoctonia solani in basil (Ocimum basilicum L.). The basil seeds treated with two Trichoderma species were planted in infested soil with R. solani and plant growth and severity of damping off measurement 40 days after planting. Peroxidase activity, total phenolic and malondialdehyde compounds levels were evaluated by colorimetic assay. The results show that eed treatments with two Trichoderma species significantly increased height and dry weight of seedling shoots and root dry weight, but their effects were not significantly different on stem diameter. Two Trichoderma species significantly reduced the severity of damping off disease where the percentages disease reduced from 71.25% in infected plants to 8.75-15.75% in plants treated with fungal anthagonists. The best protection to damping off disease was obtained by T. harzianum. Trichoderma species and Rhizoctonia solani individually increased peroxidase activity and total phenolic compounds levels, but they are more pronounced in the case of applying of combination of two fungi (Trichoderma and Rhizoctonia) in comparision to the control. Experiments indicated that maximum level of total phenolic compounds is induced by T. viride. Changes in malondialdehyde concentration occurred only in infected plants without antagonists treatments. Findings indicate that the growth and defense responses of basil significantly enhanced by seed coated with a Trichoderma different species.

Plant growth promoting (PGP) bacteria not only improve plant growth and yield but also increase plant resistance to biotic and abiotic stresses. Culture design in fermentation process has critical effect on biomass production and efficacy of these bacteria. In this work, effect of some of carbon sources have been investigated on biomass production and efficacy of Bacillus pumilus against Rhizoctonia solani, the causal agent of bean damping-off. Effect of carbon sources, glucose, molasses, brown sugar, corn meal and rice meal, in three concentrations have been examined on B. pumilus INR7 biomass production and suppression on bean damping-off in greenhouse. The highest biomass production achieved in 20 g/L of glucose and brown sugar, respectively. Increasing glucose concentration decreased biomass production but enhanced plant growth factors and the highest plant growth have been recorded in 40 g/L as the highest concentration of glucose. Molasses also increased PGP efficiency at its mid concentration, 20 ml/l. Effect of carbon sources on biocontrol efficacy of B. pumilus INR7 exhibited that glucose at 40 g/L led to the lowest root and crown infection. Molasses in 20 and 40 ml/l showed noticeable effect on biocontrol efficacy of B. pumilus INR7. In conclusion, glucose and molasses had highest effect on biomass production and biocontrol efficacy of B. pumilus INR7.

The expression of defensive genes from a promoter that is specifically activated in response to pathogen invasion is highly desirable for engineering disease-resistant plants. In this study, chimeric chitinase gene under the control of SP-DDEE pathogen inducible promoter transformed to the canola plants and these plants were evaluated for their in vivo biocontrol potential against fungal pathogens. In this regard, three constructs, pGDEC, pGMPC, pBISM2 containing synthetic promoters, SP-DDEE (two D and two E elements minimal promoter), SP-MP (minimal promoter), and the CaMV35S constitutive promoter, respectively were used. Enzyme activity assay demonstrated that the synthetic pathogen-inducible promoter was responsive to the Methyl jasmonate (MJ) elicitor, but not responsive to the salicylic acid. Moreover, results indicated that leaf total protein from transgenic lines harboring the SP-DDEE promoter treated with MJ, inhibited the growth of the fungal pathogens of Sclerotinia sclerotiorum and Rhizoctonia solani. Overall, data show that not only the SP-DDEE synthetic promoter is highly responsive to MJ, as an important chemical signal in necrotrophic pathogen defense, but the inducible expression of the chimeric chitinase gene, when controlled by the SP-DDEE promoter, is also seems to be appropriate to increased resistance to fungal pathogens.

Potato is one of the most important food and economic crops in all over the world, Rhizoctonia solani, the causal agent of stem canker causes high loss of the product quality and quantity annually. In this study, the effects of two essential oils of Thyme and Carum, were investigated on the colony growth rate and inhibitory growth in concentrations of 100, 200, 300, 400 and 500 ppm on PDA medium. In vitro tests, essential oils of thyme and Carum in two concentrations of 0.5 and 0.75, the combination of thyme 0.25+ Carum 0.25 and Rovral-Ts fungicide at 1.5 at 1000 were evaluated in a completely randomized block design in four replications. The tubers substratum cultivated in soil contaminated by R. solani that planted in pots were inoculated by essential oils and fungicides. The disease severity data were recorded and scored six weeks after inoculation using Das scale. The results demonstrated that fungal growth rate under treatment by Thyme at 500 ppm (21.63 mm /day) and Carum (17.7 mm/day) and thyme + Carum (67.85) essences were more than 50 percent growth inhibitory. The results of disease severity index in greenhouse revealed that Thyme and Carum essences and Rovral-Ts fungicide respectively by 28.1, 35.92 and 17.17 percent were successful in disease control as well as the mean of fresh and dry weight of shoot area under Thyme treatment increased relatively.